1. Field of the Invention
The present invention relates to adapter topologies, and more particularly, to adapter topologies that generate information related to available or maximum adapter current and to electronic devices configured to receive this information. Particular utility for the present invention is in portable electronic devices, however, the present invention is equally applicable to any device that uses an adapter to derive power.
2. Description of Related Art
Most portable electronic devices (e.g., portable computers, cell phones, PDAs, etc.) in use today utilize an AC/DC or DC/DC adapter that can be plugged into a wall outlet or cigarette lighter, etc., used to power the device, and possibly charge the batteries simultaneously. A typical adapter simply supplies power, and provides no information to the charger circuit as to the maximum available power that can be delivered by the adapter. To control the power delivered to the batteries (for charging) and to the device, a charger circuit is provided which regulates the flow of current from the adapter. An example of charger topologies are provided in U.S. Pat. Nos. 6,246,215 and 6,329,796; and U.S. patent application Ser. No. 09/948,828, titled “Voltage Mode High Accuracy Battery Charger”, all assigned to 02Micro International Limited, and incorporated by reference herein in their entirety. Such charger topologies dynamically allocate available adapter current between the batteries and the device.
FIG. 1 depicts a conventional topology that includes an adapter 1 and mobile equipment 2. The terms “mobile equipment” or “portable electronic device” as used herein mean a portable computer, cell phone, PDA, and/or any other device that uses an adapter to derive power. The adapter 1 generates a signal 90 indicative of the type of adapter used. This signal only has two states, and is used as an identification (ID) signal that represents the type of adapter used. The adapter 1 of FIG. 1 can be of two types: a high power adapter (e.g., 70W) or a low power adapter (e.g., 45W). The high power type of adapter generates no signal 90, while the low power adapter generates a signal 90 having a predetermined value. The mobile equipment is adapted with a switch 4, whose conduction state determines the type of adapter (low power or high power) present. Assuming that high power adapter is present, switch 4 is OFF. If a low power adapter is present, signal 90 turns switch 4 ON. Signal 90 is a signal representing the type of adapter present (low or high), and may be used by power management processors or charger circuits. Note that this topology only has two states representing the presence of a low power adapter or high power adapter, and thus cannot generate information related to the maximum or available power provided by the adapter. Note also that this topology requires that the adapter and mobile equipment be matched, such that the adapter could not be used with other mobile equipment and vice-versa.
Thus, there exists a need to provide an adapter topology that provides information related to maximum adapter current, which may be utilized by a charger to accurately allocate available current to batteries (for charging) and a device (for operation). There also exists a need for an adapter topology that permits the adapter to be used with a wide range of devices so that the adapter is can be used with many types of mobile equipment devices.